A water quality sensor includes a housing including a light transmissive bucket mounted in an electrical washing appliance and a light transmissive inner barrel mounted in the bucket, an actuation module mounted in the inner barrel for detecting a water quality of a washing solution in the electrical washing appliance. Thus, if the bucket is cracked during manufacturing or due to a collision, the actuation module can still be well protected by the inner barrel, so that the washing solution in the electrical washing machine does not directly flow into and contact with the actuation module to cause an accidental short circuit of the circuit substrate of the actuation module, improving the water resistance and service life of the water quality sensor.